HISTORY OF ANTI HUMAN GLOBULIN
Moreschi was first to described the use of Anti-human globulin in 1908. (Moreschi 1908). Moreschis studies involved the use of rabbit anti goat antiserum to agglutinate rabbit red blood cells that were sensitized with low non-agglutinating dose of goat anti rabbit red cell serum. Coombs rediscovered the test in 1945 (Coombs et al., 1945; Coombs et al., 1946) By injecting rabbits with human IgG, they were able to produce a protein (Anti-IgG) that reacted with incomplete antibodies
(IgG). They also described the use of anti human globulin test to detect in vivo sensitization of red blood cells in babies suffering from haemolytic disease of the newborn. Although the test initially was of great value in investigating RhO(D) haemolytic disease of the newborn, it was not long before its versatility for the detection of other IgG blood group antibodies became evident.
TYPES OF ANTI HUMAN GLOBULIN
The classic method of AHG production involves injecting human serum or purified globulin into laboratory animals such as rabbits or goats. The human globulin behaves as foreign antigen, the rabbit’s immune response is triggered and an antibody to human globulin is produced. For example, human IgG injected into a rabbit results in anti-IgG production; human complement components injected into a rabbit result in anti complement. This type of response produces a polyclonal antiglobulin serum. Hybridoma technology can be used to produced monoclonal antiglobulin serum.
Hence, AHG can be classified into two namely;
- Polyspecific antihumanglobulin which include
- Polyclonal antihumanglobulin
- Monoclonal antihumanglobulin
- Monospecific antihumanglobulin
Antibodies Involved in Polyspecific Anti human globulin
In polyspecific antihumanglobulin, it contains antibody to human lgG and to the C3d component of human complement. Other anti complement antibodies such as anti -C3b, anti-C3b, anti-C4b and anti-C4d, may also be present. Commercially prepared polyspecific anti-human globulin contains little, if any activity against lgA and lgM heavy chains. However, the polyspecific mixture may contain antibody activity to kappa and lambda light chains common to all immunoglobulin classes, thus reacting with lgA or lgM molecules. (Brechest 2002).
Antibodies involved in monospecific anti human globulin
The monospecific AHG reagents contain only one antibody specificity either anti-lgG or antibody to specific complement components such as C3b or C3d. licensed monospecific antihumanglobulin reagents in common use are anti-lgG and anti-C3b-C3d. (Brecher, 2002).